3.2.5. SEM observation of the fractured surface in UHMWPE fi bers/
NR composites
Fig. 10 shows the SEM images of the fractured surfaces of asreceived and treated UHMWPE fibers/NR composites, which
reflect the structural integrity and the adhesive features of the
compositions in the composites. It can be evidently observed that
for as-received UHMWPE fibers/NR composites, many fibers are
pulled out from natural rubber (Fig. 10(a)) and UHMWPE fiber is
rather clean with almost no distinct interfacial bond (Fig.10(b), (c)),
showing poor interfacial adhesion. This is because as-received
UHMWPE fibers with surface inertness cannot well bond with
NR. However, in Fig.10(d), it can be seen that less fibers were pulled
out from matrix and the failure of the treated UHMWPE fibers/NR
composites was accompanied by several micro-fibrillation of the
fiber (as the arrows showed in Fig. 10(e), (f)), indicating UHMWPE
fibers are better bonded with NR. Such better interface bond should
be attributed to that the chemical activity of the hydroxyl group on
the surface of treated UHMWPE fibers promotes the adhesion between UHMWPE fibers and NR. Due to the effect of increased
amount of hydroxyl group on the surface of treated UHMWPE fi-
bers, UHMWPE fibers are bonded with NR [28].